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Q&A: General Astronomy and Space Science

Q:
Every picture of a spiral galaxy including our own, depicts a very bright, spherical center ... I assume a dense cluster of stars. We can see this bright center in distant galaxies, and I've always wondered, why we don't see the bright center of our own. Or, do we, and I don't know what I'm looking at? It seems it would be far brighter than our Sun, even though we are at the far edge of the galaxy. Thanks for helping me find it!!

A:
There is a spherical region surrounding the central region of our galaxy known as the "bulge" which is indeed dense with stars. It is actually more luminious than it appears because its light is diminished by absorption from dust as well as distance by the time it reaches us. The Earth is situated in the middle of the plane of our galaxy where the absorption towards the center is maximum. The surface brightness, or brightness per angular area, of the bulge is much less than the Sun's because of this absorption and the fact that the stars, though dense, still fill only a small fraction of the volume.

The galaxies that appear in the astronomy books are selected because they are the most photogenic and are generally not typical. We look at them face on which is a viewing direction where there is little absorption.

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